The Influence of Pulsating Throughflow on the Onset of Electro-Thermo-Convection in a Horizontal Porous Medium Saturated by a Dielectric Nanofluid

The joint effect of pulsating throughflow and external electric field on the outset of convective instability in a horizontal porous medium layer saturated by a dielectric nanofluid is investigated. Pulsating throughflow alters the basic profiles for temperature and the volumetric fraction of nanoparticle from linear to nonlinear with layer height, which marks the stability expressively. To treat this problem, the Buongiorno’s two-phase mathematical model is used taking the flux of volumetric fraction of nanoparticle is vanish on the horizontal boundaries. Using the framework of linear stability theory and frozen profile approach, the stability equations are derived and solved analytically applying the Galerkin weighted residuals method with thermal Rayleigh-Darcy number as the eigenvalue. The effect of increasing the external AC electric Rayleigh-Darcy number , the modified diffusivity ratio and the nanoparticle Rayleigh number is to favorable for the convective motion, while the Lewis number and porosity parameter have dual influence on the stability scheme in the existence of pulsating throughflow. The frozen profile method shows that the result of pulsating throughflow in both directions is stabilizing. An enlarged amplitude of throughflow fluctuations offers to increased stability by an amount that vary on frequency. It is also found that the oscillatory mode of convection is not favorable for nanofluids if the vertical nanoparticle flux is vanish on the boundaries.

کلیدواژه ها:

Nanofluids ، Pulsating throughflow ، Linear stability theory ، convection ، Electro ، Galarkin method